[ax + b₂y=c₁
fax+by=ci 可用向量線性組合改寫為x
x=2.y3為方程組的解∴OA+3OB-OC
OA-(a, as) OB (b, b) OC (2a,+3b,. 2a, +3b₂)
BA (a, b, ay-b₂) BC (2a,+2b, 2a,+2b₂)
△ABC 面積
△OAB面積
1 a, b, 2a, 2b,
2 a b 2a+2b
1 a
,亦即xOA+yOB = OC
a b
a₁-b₁ a₁+b₁
21
a-by
ab
b₁
a b
2a,
a+b₁
2
2a
4
a ab₁
a
a+b
4
by
a
a+b₁₂
a
b
a
b₁
a b₁₂
a b
az b
a
by
故選(4)
az b₂